2,4,6-tri-tertiary-butyl phenol



Patented July 8, 1941 zss-rm-rrarmnrmom manor.

Donald 8. Stevens, Swissvale, and William A. Gruse, Wilkinsburg, Pa... assignors to Gulf Oil Cowman, Pittsburgh, Pa., a. corporation of Pennsyl No Drawing. Original application April 12, 1937,

Serial No. 136,504. Divided and this application January 16, 1939, Serial No. 251,281

I Claim. (01. 260-624) This invention relates to tri-alkylated monolwdroxy phenols and more particularly to 2,4,6- tri-tertiary-butyl phenol, a compound which is soluble in oil and insoluble in dilute aqueous alkali solution and which possesses the property of inhibiting oxidational changes in petroleum hydrocarbon products when added thereto in relatively small amounts all as more fully hereinafter set forth and as claimed.

This application is a division of our copending application for United States Letters Patent Serial No. 136,504, filed April 12, 1937, now matured into Patent No. 2,202,877, issued June 4,

In our earlier filed applications Serial Nos. 649,670, filed December 30, 1932, and 702,258, filed December 13, 1933, now U. S. Patent 2,061,111, we have'described' and claimed the manufacture of anti-oxidants and the addition thereof to motor fuels, which anti-oxidants are obtained by treating low boiling cracked distillates, such as cracked gasoline containing olefins such as propylene and butylene, with aryl-hydroxy compounds such as phenol, cresols or xylenols at a relatively low temperature in the presence of an acid condensing agent or at a relatively high temperature in the absence of an acid condensing agent. In our copending application Serial No. 110,014, filed November 9, 1936, which is a division of application Serial No. 702,258, we have described and claimed antioxidant materials as thus produced and hydrocarbon products containing them.

After considerable research we succeeded in identifying the chemical character of certain of the constituents of the antioxidant materials described and claimed in our aforesaid applications, and in our application Serial No. 136,504, filed April 12, 1937, which is a continuation-inpart of the previously filed applications referred to hereinabove, we have described and claimed for use as antioxidants, particularly for petroleum oils, a class'of compounds consisting of the 2,4,6-tri-alkylated monohydroxy phenols having in a position ortlio to the hydroxyl group at least one alkyl substitution group having three or more carbon atoms, e. g., a propyl, butyl, amyl, or higher alkyl group, the remaining alkyl groups being similar or different, for example methyl, ethyl or higher alkyl groups, which are soluble in oil and insoluble in dilute aqueous alkali solution and in water. The present application is concerned with one of the compounds of this newly discovered class, disclosed in said application Serial No. 136,504, namely, 2,4,6-

tri-tertiary-butyl-phenol which we have synthesized in substantially pure form.

We have discovered that by alkylating phenol v with isobutylene until no more isobutylene condenses with the phenol, we can produce 2,4,6- tri-tertiary-butyl-phenol, a compound which is soluble in oil and insoluble in dilute aqueous alkali solution. We have discovered also that this compound possesses good antioxidant properties and when added to organic materials, especially petroleum oil products such as gasoline, lubricating oils, transformer oils, turbine oils and the like, in relatively small amounts it stabilizes these materials against oxidational changes.

In preparing 2,4,6-tri-tertlary-butyl-phenol isobutylene either alone or in admixture with other hydrocarbons may be used to alkylate the phenol. Cracked gasoline as normally produced and the heavier of the hydrocarbons usually found as vapors in cracking-still'gases contain varying quantities of isobutylene as well as higher olefins and may be used as starting materials.

0n the other hand, the isobutylene may be used in isolated form or in admixture with other closely related olefins or paraflins. For example, so called debutanizer gas may be employed as a starting material as may isobutylene itself. It will be readily understood that when it is desired to prepare 2,4,6-tri-tertiary-butyl-phenol, free or substantially free from other compounds, the raw material should not comprise mixtures of olefins or mixtures of phenols except in those cases in which the natures of the individual products will permit easy isolation and separation after alkylation. As to mixtures of isobutylene and parafllns such as butane, the presence of the paraflin has no effect on the operation other than to reduce the concentration of the isobutylene; the butane does not enter into the reaction with the phenol.

In general the methods set forth in our prior applications referred to hereinbeiore, may be employed in preparation of 2,4,6-tri-tertlarybutyl-phenol, wi h due regard to the selection of the raw materials. Thus at temperatures up to F. or thereabouts and under atmospheric or moderately elevated pressures the usual condensing agents are employed, including sulfuric acid, phosphoric acid, anhydrous aluminum chloride, boron tri-fluoride, ferric chloride, hydrogen chloride and the like. Sulfuric acid is ordinarily most satisfactory by reason of its efliciency and cheapness. The amount of acid condensing agent required is relatively small with respect to. the

amount of phenol; in some instances the amount of acid condensing agent required is as little as 1 per cent of the phenol or less, being in such instances present in catalytic amounts. In using sulfuric acid as the condensing agent and when it is desired to utilize the isobutylene emciently. it is usually better to employ the acid in an amount equal to not less than about 3.0 per cent of the phenol. More than 10 per cent of the condensing agent, based on amount of phenol is not ordinarily worth while. At higher temperatures and pressures, for example from about 400 to 575 F. or higher, and 1000 pounds per square inch or somewhat higher, condensing agents are sometimes unnecessary and may be omitted. The temperatures should not be so high as to cause decomposition of the phenol. It is ordinarily advantageous to avoid temperatures and pressures so high that the product obtained will predominate in polymerized isobutylene, the formation of which is enhanced by heat and pressure.

The reaction involves no special difficulties, the reacting ingredients being simply contacted in the usual manner either continuously or in batch operation. After completion of the reaction the products are usually washed with an aqueous solution of caustic soda or other equivalent alkali, the strength of the washing solution being preferably not over 15 per cent. This washing operation removes any remaining acid condensing agent and also removes all alkali soluble material, such as any unreacted phenol, as well as alkylation products in which. the alkylatiDn has not proceeded to the point desired. Water washing may also be resorted to wherever desired. The washed product may then be distilled under ordinary pressure or under vacuum and recrystallized in the usual manner to separate the by-products and obtain substantially pure 2,4,6-tri-tertiary-butyl phenol.

While the methods set forth in our previously filed applications are generally applicable for the preparation of the compound described and claimed herein, other methods of synthesizing this compound may be resorted to when desired. For example, 2,4,6 -tri-tertiary-butyl phenol may be prepared from 2,4-di-tertiary-butyl phenol by reaction with tertiary butyl chloride in the presence of metallic sodium, as set forth hereinbelow. Other methods of synthesis applicable to the various compounds will doubtless suggest themselves to those skilled in the art.

The following examples will serve to illustrate and exemplify our invention.

Example 1.--In this example, 2,4,6-tri-tertiarybutyl phenol was prepared from phenol and isobutylene gas in the presence of sulfuric acid. We find it advantageous to employ ordinary concentrated sulfuric acid in amounts corresponding to from 3 to 5 per cent by weight of the phenol employed; with this concentration the rate of condensation is sufficiently high, while with higher amounts of acid the tendency toward polymerization of the isobutylene is increased, We may also state that we find it advantageous in obtaining a major proportion of the desired product in the total products of reaction to maintain the reaction temperature at about 50 C., during the first period of condensation, until the condensation products form a magma or mush, after which we find it desirable to raise the temperature enough to retain the reaction mass in a more or less liquid condition, thereby facilitating contact between the reacting materials.

25 parts by weight of commercial concentrated sulfuric acid were introduced into a suitable reaction vessel provided with a gas inlet and a gas outlet, suitable agitating means. and a coil for heating or cooling thecontents of the reaction vessel. Isobutylene was then bubbled through the phenol, which was maintained at a temperature of- 50 C., with agitation, until the reaction mixture took on the appearance of a magma, when the temperature was raised to 100 C. In this example the pressure was atmospheric.

After the reaction had been substantially completed, as indicated by the fact that the reaction mixture no longer gained in volume and by the flow of isobutylene at the gas exit, the flow of gas was stopped. The reaction mixture was washed with water until neutral. It was then distilled in a column under 10 mm. pressure. The lower boiling fractions thus obtained consisted largely of para-tertiary-butyl phenol and 2,4-di-tertiarybutyl-phenol while the remaining fraction consisted almost entirely of 2,4,6-tri-tertiary-butyl phenol boiling at 140 C. under 10 mm. pressure. This fraction amounted to approximately 65 per cent of the total washed reaction product. On cooling, this fraction solidified to white crystals having a melting point of 130 to 131 C. After crystallization from alcohol, the following constants were obtained for the substantially pure product.

a t??? am or Found tri-tertiarybutyl phenol Melting point, C 180-131 Ultimate analysis, percent by weight:

Carbon 82 35 82. 44 Hydrogen ll. 40 11. 45 6. 25 6. 11

As an alternative method of procedure, the reaction product may be washed with dilute aqueous caustic soda solution to separate the monoand ditertiary-butyl phenols, distillation and recrystallization otherwise proceeding as indicated.

The product obtained in accordance with the foregoing example is an excellent gasoline antioxidant, readily and cheaply preparedAnsoluble in water and in dilute caustic solution, and having a high antioxidant effect, as indicated by a standard oxygen stability test (Hunn, Fisher 6:

Thus, 500 parts by weight of phenol (USP) and Blackwood, J. Soc. of Automotive Engineers, vol. 26, page 31, 1930), in whichthe stability of the fuel against oxidation is measured in terms of induction period and the higher values indicate the more stable fuels.

In determining the antioxidant value of this compound, standard reference fuels were employed, for example, a refinery gasoline obtained by blending pressure distillate, reformed naphtha distillate and straight-run gasoline. The reference fuels employed were uninhibited by the addition of other antioxidants and contained no lead tetra-ethyl. Two standard reference fuels of the character indicated, when tested by the stability test referred to hereinbefore, showed induction periods or-stability periods of 1 and 1%, hours, respectively. The same fuels, when inhibited by the addition of 0.04 gram of 2,4,6-tritertiary-butyl phenol, prepared as indicated above, per cc. of the fuel, were found to have induction periods of 5V; and 6 hours, respecoxidant by a standard testing method. Moreover, the same product was found to restrain oxidation of such highly refined oils as the so-called white oils, medicinal oils and agricultural spray oils, when added thereto in small amount, as determined by a standard test indicating the behavior of such oils when exposed to sunlight.-

The same compound when incorporated in amount between- 0.1 and 0.5 per cent in highly refined automotive lubricating oils, exerted a marked antioxidant efiect, stabilizing the lubricants against color changes and other deterioration when subjected to temperatures corresponding to those to which such oils are subjected in actual use. Example 2.-In this example 2,4,6-tri-tertiarybutyl phenol was prepared by a different method. 90.8 parts by weight of 2,4-di-tertiary-butyl phenol were added to a solution of 10.5 parts by weight of metallic sodium in 89 parts by weight of absolute alcohol, after which 52 parts by weight of tertiary-butyl-chloride were added and the mixture was gently refluxed for twenty hours. After filtering ofl sodium chloride from the cooled mixture, the solid was washed thoroughly with absolute alcohol, the washings being added to the filtrate which was then concentrated under reduced pressure in a water bath at 63 C. to -remove alcohol and any remaining tertiarybutyl-chloride. The residue was taken up with hexane, the hexane solution being first washed with per cent aqueous sodium hydroxide solution and then with solutions of increasing concentrations of alkali, up to 40 per cent NaOH. Some alkali-soluble material was removed in the weak alkali washings. When the concentration or alkali reached per cent the sodium salt of 2,4-di-tertiary-butyl phenol began to precipitate. The alkali extraction was. continued until no I more precipitate was obtained, the solids being filtered off after each extraction and washed thoroughly with hexane. 63.1 parts by weight of 2,4-di-tertiary-butyl phenol were recovered upon subsequent hydrolysis of the solid sodium salt. The alkaline washes did not remove the 2,4,6-tri-tertiary-butyl phenol from solution with hexane.

After extraction, the hexane solution was washed free from alkali, the hexane was distilled oil, and the residue, amounting to 21.9 parts by weight, was distilled at atmospheric pressure. The boiling range was 265 C. to 280 C. with most of the fraction distilling below 271 C. The distillate solidified on cooling to'an oily crystalline mass having a brilliant orange color, the yield being 15.8 parts by weight. After three crystallizations from alcohol, pure white crystals were obtained melting between and 131 C. Further crystallization did not alter the melting point. These crystals were found to give constants substantially identical to those obtained for the product obtained in accordance with the process set forth under Example 1, and consist of substantially .pure 2,4,6-tri-tertiary-butyl phenol. The antioxidant and other properties of this product were, of course, found to be substantially identical with those of the product obtained in accordance with Example 1.

While we have described our invention hereinabove with respect to various specific illustrative examples, it will be obvious that our invention" is not limited to the details of such examples, but may be variously practiced and embodied within the scope of the claim hereinafter made.

It will also'be understood that our invention is I 

